Antihalation film



Patented Feb. 16, 1943 .m'mmm'rron mm Gale F. Nadeau and Alfred Di-slack, Rochester, N. Y., asslgnors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application March 4, 1941, Serial No. 381,695

7 Claims.

This invention relates to a photographic film and more particularly to a film provided with antihalation layers.

Coatings on the backs of films containing a dye or a superficial dye layer removable in photographic processing solutions are well known for antihalation purposes. Less well known are antihalation layers which are designed to be non-removable. The disadvanta es of the removable types-of coatings are the tendency of some coatings to deposit sludge in processing solutions, the tacky nature of some coatings, the known thermoplastic qualities of other coatings which are in general undesirable, and furthermore, in the case of-certain resinous coatings their tendency to form insoluble products with the antihalation dye. Non-removable antihalation layers have been designed to avoid these difliculties and to prevent the penetration of the dye into and the consequent staining of the support. The success of this practice depends upon the selection of a material, for the dye carrier, which is sufiiciently permeable to processing solutions, yet not soluble, that the dye giving antihalation protection may be completely discharged when desired.

slon layer adhesively joined to the support by The object of the present invention is to provide a photographic film with a carrier for an antihalation dye, said carrier being permeable to, but not soluble in, photographic processing solutions. Other objects appear hereinafter.

We have found that a cellulose ester containing substantially 4-8 acyl groups per C24 cellulose unit, of which not more than one is a dicarboxylic acid acyl group and the remainder are aliphatic monobasic acid acyl groups of less than five carbon atoms, accomplishes our objects when used as an antihalation layer in conjunction with a dye.

The general method we employ is to-coat a photographic support with an emulsion, joining said emulsion to the support by means of suitable subbing layers. We then "coat a water-permeable cellulose ester layer and a dye layer onto the other side of the support. We may vary this procedure .by applying the antihalation layer between the light sensitive emulsion layer and the support. The antihalation layer may also be coated before the emulsion layer. a

In the accompanying drawing are shown number of enlarged sectional views of photographic supports provided with'an antihalation layer according to our invention. In the drawing:

means of'a subbing layer, and on the opposite side, a cellulose acetate antihalation layer containing a dye.

Fig. 3 represents a multi-layer color film provided, on one side of a subbed cellulose acetate propionate support, with emulsion layers sensitive to red, green and blue light, and on the opposite side, a cellulose acetate phthalate antihalation layer containing a dye.

According to the preferred method of our invention we use an antihalation layer consisting of cellulose esters containing substantially 4-8 acyl groups, but not more than one dicarboxylic acid acyl group per Cu cellulose unit, in intimate contact with a dye layer. We have particularly chosen cellulose esters of this range of acyl content because of their characteristic permeability to water. For instance, cellulose acetates containing more than 8 acyl groups per C24 cellulose unit are not sumciently permeable to aqueous photographic processing solutions to allow quick and complete removal of antihalation dyes. Cellulose acetates containing less than 4 acyl groups per C24 unit are generally too permeable to water, in fact, may be too soluble in water to be of use as components of antihalation layers which are intended to be non-removable. The cellulose ester need not contain any dicarboxylic acid acyl group, provided that it contains 4 to 8 non-dicarboiwlic acid acyl groups. If, however, one of the acyl groups is a dicarboxylic acid acyl group, the ester will contain only 3 to? non-dicarboxylic acid acyl groups. It is obvious that we contemplate the use of other cellulose esters or mixed esters such as cellulose acetate propionate, cellulose acetate propionate phthalate, cellulose acetate butyrate phthalate, cellulose acetate butyrate, cellulose acetate phthalate, cellulose acetate succinate, etc., the acyl content of which is of the order described. That is, different esters such as cellulose acetate and cellulose butyrate having the same acyl content would have different permeabilities .in respect to water, and could not be properly identifled in terms of weight percent of acyl without excluding members of the group of cellulose esters we may use, and including others we do not contemplate in our invention. In a similar manner we designate cellulose mixed acid esters according to their acyl content. Thus, cellulose acetate phthalates containing 4 to 8 acyl groups but not more than one dicarboxylic acid a y sm n P Ca unit are contemplated for use in our invention. Esters-of this class containing less than 4 acyl groups or more than one phtbalyl group per Cu unit are too soluble in photographic processing solutions to be of use in the manner of our invention. Likewise those containing more than 8 acyl groups are too impermeable to be used in our invention. Similarly, esters of aliphatic monobasic acids of more than four carbon atoms are not contemplated in our invention.

In designating the cellulose esters of our invention in terms of acyl groups, we use the expression substantially." This is due to the fact that in analyzing our esters we find that those esters which are useful fall within the range approximated by those esters having 4 to 8 acyl groups per C24 cellulose unit. Thus, a cellulose acetate, 34% acetyl, ha about 8 acetyl units per Ca cellulose unit-acetates containing more than this amount of acetyl are not useful in our invention. Cellulose acetate containing less than about 20% acetyl is too permeable to water to be useful in our invention and this analysis corresponds rather closely to 4 acetyl groups per C24 unit.

Of the mixed esters of cellulose the same is true. Cellulose acetate phthalate containing more than about 14% phthalyl, in addition to about 7 acyl groups per C24 unit is too permeable to photographic developing solutions to be of use in our invention and this phthalyl content corresponds to about one phthalyl group per Cu unit of cellulose. We use a C24 unit as the basic cellulose unit in order to avoid expressing the dicarboxylic acid acyl content of an ester in fractional terms in respect to the aliphatic monobasic acid acyl content.

Several types of supports may be provided with the antihalation layer of our invention. Cellulose esters such as cellulose acetate or nitrate, or mixed esters of cellulose, such as, cellulose acetate propionate and celulose acetate butyrate,

and opaque supports such as paper, may all be so provided with antihalation layers. Dyes which are removable in ordinary photographic processing solutions are applicable for use in conjunction with the cellulose ester antihalation layers we describe. These dyes are commonly known as fugitive dyes. The dye may be applied to the antihalation carrier layer by dispersing it in an organic solvent such as a mixture of methanol and water; or ethanol, water and methyl Cellosolve in suitable proportions. 7

We will now describe our invention with particular reference to the accompanying drawing.

As shown in Fig. 1 we coat a cellulose ester support III with a subbing layer II which may be gelatin or other suitable material, and over this- Fig. 2 shows a more specific application of our invention wherein the support I! of a cellulose ester is coated with an emulsion layer II adhesively joined to the support by means of a subbing layer H such as gelatin. On the opposite side of the support is coated an antihalation layer I 2 of a cellulose acetate, 21-36% acetyl, containing a dye in the outer stratum.

Fig. 3 shows a multi-layer color film wherein a cellulose acetate propionate support II is provided with the red, green and blue light sensitive emulsion layers II, II and I8, respectively, adhesively joined to the support by means of a subbing layer 14. On the opposite side of the support is an antihalation layer ll consisting of a cellulose acetate phthalate, 14-28% acetyl and 044% phthalyl, containing a dye.

The following examples illustrate several methods of producing a film according to our invention.

Example I A film base of cellulose acetate containing 38-42% acetyl is coated with a 3% solution of cellulose acetate, acetyl content 33%, from a mixture of 10 parts of water, 45 parts of acetone, and 45 parts of methanol. Over this layer is applied a fugitive type of dye such as Acid Blue 2B. or a dye of Color Index No. 702, 704, 705, or 707. The solvent mixture for the dye may vary over a fairly wide range, although a mixture of parts of methanol and 10 parts of water is generally satisfactory. Another solvent solution for the cellulose acetate backing layer may consist of 7% water, 83% acetone and 10% methyl Cellosolve.

On the other side of the film, is coated from solvent solution, a subbing layer consisting of a resin or a mixture of a resin and a cellulose ester followed by a gelatin layer and a light sensitive emulsion layer. The use of resin containing subbing layers has been more fully described in a prior patent U. S. 2,133,110 and others. A subbing solution. containing gelatin, and which is suitable for coating a gelatin layer over a resin containing layer is also described therein.

Example 2 A film base of cellulose acetate propionate containing 16% propionyl and 29% acetyl is coated with a 3% solution of cellulose acetate phthalate, acetyl content 25% and phthalyl 13%, in a mixture of 45 parts acetone and 55 parts of methanol. A ,dye is applied over this layer in the manner described in the preceding example penetrating the layer to a limited extent. On the other side of the support, now provided with an antihalation layer, are coated resin containing and gelatin subbing layers in the manner described in the prior patent cited. We then provide the film with differentially light sensitive emulsion layers which may be sensitized in the natural order and colored complementary to the sensitivity as shown in Fig. 3 of the drawing. A filter dye may be incorporated in one of the layers such as the bluesensitive layer in order to screen the lower layers from radiations which they are not intendedqto record. Also, there may be interposed between the emulsion layers a layer designed to receive a sound record or this record may be printed in one of the emulsion layers. It is obvious that we may reverse or vary the order of deposition of the layers on the support as in an alternative method we coat the emulsion layers on the support before the antihalation and dye layers.

Example 3 I tone. Over this is applied a dye such as Acid Blue 3R from a solvent solution containing 2.5% dye in a. mixture of 80% methyl alcohol and 20% water. Similarly, we add to the dye coating solution of the weight of the dye of a basic material such as triethanolamine, diethyl aminoethanol, ammonia, dloctylamine, tributylamine, diamylamine, etc.

The photographic elements-described in the foregoing examples are used in any of the well known processes designed to record an image in black-and-whlte or color. After exposure of the materials to an image the elements are usually developed to a negative and during this development or in a subsequent fixing treatment the cellulose ester antihalation layer becomes sufliciently swollen to allow the penetration of the constituent removing the antihalation dye, but the cellulose ester layer is not dissolved.

While we have described the use of permeable cellulose esters in antihalation layers, and this is the preferred embodiment of our invention, it is evident that any process requiring a water permeable, but not soluble layer, with or without a dye, may be served by the materials of our invention. Such processes are those of the photographic type which use sensitive films containing light filtering layers, the dye of which is to be removed at some stage in the processing treatment.

The materials and examples of the present specification are illustrative only and it is to be understood that numerous methods and ingredients may be used within the scope of the present description, and that the scope of our invention is to be taken as limited only by the scope of the appended claims.

What we claim is:

1. A photographic element free from halation which comprises a support provided with a light sensitive emulsion layer, and an antihalation layer of a water-permeable cellulose ester containing substantially 4 to 6 acyl groups per 24 cellulose unit, of which all are aliphatic monobasic acid acyl groups of less than flve carbon atoms, said layer carrying a light-absorbing dye.

which comprises a support provided with a light sensitive emulsion layer, and an antihalation layer of a water-permeable cellulose ester containing substantially 4 acyl groups per C24 cellulose unit, said layer carrying a light-absorbing dye.

3. A photographic element free from halation which comprises a support provided with a light sensitive emulsion layer, and" an antihalation layer of a water-permeable cellulose ester containing substantially 4 acetyl groups per C24 cellulose unit, said layer carrying a light-absorbing dye.

4. A photographic element free from halation which comprises a cellulose acetate support provided with a light sensitive emulsion layer, and an antihalation layer of a water-permeable cellulose ester containing substantially 4 acetyl groups per C24 cellulose unit, said layer carrying a light-absorbing dye.

5. A photographic element free from halation which comprises a support provided with a light sensitive emulsion layer, and an antihalation layer of a water-permeable cellulose ester containing substantially 6 acyl groups per C24 cellulose unit, said layer carrying a light-absorbing dye.

6. A photographic element free from halation which comprises a support provided with a light sensitive emulsion layer, and an antihalation layer of a water-permeable cellulose ester containing substantially 6 acetyl groups per C24 cellulose unit, said layer carrying a light-absorbing dye.

'7. A photographic element free from halation which comprises a cellulose acetate support provided with a light sensitive emulsion layer, and an antihalation layer of a water-permeable cellulose ester containing substantially 6 acetyl groups per C24 cellulose unit, said layer carrying a light-absorbing dye.

' GALE F. NADEAU.

ALFRED D. SLACK. 

